Systems Analysis and Design in a Changing World, Fourth Edition

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Systems Analysis and Design in a
Changing World, Fourth Edition

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Systems Analysis and Design in a Changing World, 4th Edition 2
Learning Objectives
Explain the purpose and various phases of the systems
development life cycle (SDLC)
Explain when to use an adaptive approach to the SDLC in
place of a more predictive traditional SDLC
Explain the differences between a model, a tool, a
technique, and a methodology
Describe the two overall approaches used to develop
information systems: the traditional method and the
object-oriented method

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Learning Objectives (continued)
Describe some of the variations of the systems
development life cycle (SDLC)
Describe the key features of current trends in systems
development: the Unified Process (UP), Extreme
Programming (XP), Agile Modeling, and Scrum
Explain how automated tools are used in system
development

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Overview
System development project
Planned undertaking with fixed beginning and end
Produces desired result or product
Can be a large job with thousands of hours of effort or a
small one-month project
Successful development project
Provides a detailed plan to follow
Organized, methodical sequence of tasks and activities
Produces reliable, robust, and efficient system

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The Systems Development Lifecycle
(SDLC)
Systems development life cycle (SDLC)
Provides overall framework for managing systems
development process
Two main approaches to SDLC
Predictive approach – assumes project can be
planned out in advance
Adaptive approach – more flexible, assumes
project cannot be planned out in advance
All projects use some variation of SDLC

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Choosing the Predictive vs. Adaptive
Approach to the SDLC (Figure 2-1)

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Traditional Predictive Approach to the
SDLC
Project planning – initiate, ensure feasibility, plan
schedule, obtain approval for project
Analysis – understand business needs and
processing requirements
Design – define solution system based on
requirements and analysis decisions
Implementation – construct, test, train users, and
install new system
Support – keep system running and improve

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Information System Development Phases

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SDLC and Problem Solving
Similar to problem-solving approach in Chapter 1
Organization recognizes problem (project planning)
Project team investigates, understands problem and
solution requirements (analysis)
Solution is specified in detail (design)
System that solves problem is built and installed
(implementation)
System used, maintained, and enhanced to continue to
provide intended benefits (support)

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“Waterfall” Approach to the SDLC

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Modified Waterfall Approach
with Overlapping Phases (Figure 2-5)

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Newer Adaptive Approaches to the SDLC
Based on spiral model
Project cycles through development activities over and over
until project is complete
Prototype created by end of each cycle
Focuses on mitigating risk
Iteration – Work activities are repeated
Each iteration refines previous result
Approach assumes no one gets it right the first time
There are a series of mini projects for each iteration

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The Spiral Life Cycle Model (Figure 2-6)

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Iteration of
System
Development
Activities
(Figure 2-7)

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Activities of Each SDLC Phase
Predictive or adaptive approach use SDLC
Activities of each “phase” are similar
Phases are not always sequential
Phases can overlap
Activities across phases can be done within an
iteration

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Activities of Planning Phase of SDLC
Define business problem and scope
Produce detailed project schedule
Confirm project feasibility
Economic, organizational, technical, resource, and
schedule
Staff the project (resource management)
Launch project official announcement

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Activities of Analysis Phase of SDLC
Gather information to learn problem domain
Define system requirements
Build prototypes for discovery of requirements
Prioritize requirements
Generate and evaluate alternatives
Review recommendations with management

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Activities of Design Phase of SDLC
Design and integrate the network
Design the application architecture
Design the user interfaces
Design the system interfaces
Design and integrate the database
Prototype for design details
Design and integrate system controls

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Activities of Implementation Phase of
SDLC
Construct software components
Verify and test
Convert data
Train users and document the system
Install the system

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Activities of Support Phase of SDLC
Maintain system
Small patches, repairs, and updates
Enhance system
Small upgrades or enhancements to expand
system capabilities
Larger enhancements may require separate
development project
Support users
Help desk and/or support team

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Methodologies and Models
Methodologies
Comprehensive guidelines to follow for completing
every SDLC activity
Collection of models, tools, and techniques
Models
Representation of an important aspect of real
world, but not same as real thing
Abstraction used to separate out aspect
Diagrams and charts
Project planning and budgeting aids

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Some Models Used in System
Development

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Tools and Techniques
Tools
Software support that helps create models or other
required project components
Range from simple drawing programs to complex
CASE tools to project management software
Techniques
Collection of guidelines that help analysts
complete a system development activity or task
Can be step-by-step instructions or just general
advice

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Some Tools Used in System Development

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Some Techniques Used in System
Development

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Relationships Among Components of a
Methodology

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Two Approaches to System Development
Traditional approach
Also called structured system development
Structured analysis and design technique (SADT)
Includes information engineering (IE)
Object-oriented approach
Also called OOA, OOD, and OOP
Views information system as collection of
interacting objects that work together to
accomplish tasks

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Traditional Approach
Structured programming
Improves computer program quality
Allows other programmers to easily read and
modify code
Each program module has one beginning and one
ending
Three programming constructs (sequence,
decision, repetition)

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Three Structured Programming Constructs

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Top-Down Programming
Divides complex programs into hierarchy of
modules
The module at top controls execution by “calling”
lower level modules
Modular programming
Similar to top-down programming
One program calls other programs to work
together as single system

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Top-Down or Modular Programming

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Structured Design
Technique developed to provide design
guidelines
What set of programs should be
What program should accomplish
How programs should be organized into a
hierarchy
Modules are shown with structure chart
Main principle of program modules
Loosely coupled – module is independent of other
modules
Highly cohesive – module has one clear task

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Structure Chart Created Using
Structured Design Technique

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Structured Analysis
Define what system needs to do (processing
requirements)
Define data system needs to store and use (data
requirements)
Define inputs and outputs
Define how functions work together to accomplish
tasks
Data flow diagrams (DFD) and entity relationship
diagrams (ERD) show results of structured
analysis

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Data Flow Diagram (DFD) Created Using
Structured Analysis Technique (Figure 2-15)

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Entity-Relationship Diagram (ERD)
Created Using Structured Analysis
Technique

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Structured Analysis Leads to Structured Design
and Structured Programming (Figure 2-17)

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Information Engineering (IE)
Refinement to structured development
Methodology with strategic planning, data
modeling, automated tools focus
More rigorous and complete than SADT
Industry merged key concepts from structured
development and information engineering
approaches into traditional approach

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Object-Oriented Approach
Completely different approach to information
systems
Views information system as collection of
interacting objects that work together to
accomplish tasks
Objects – things in computer system that can
respond to messages
Conceptually, no processes, programs, data
entities, or files are defined – just objects
OO languages: Java, C++, C# .NET, VB .NET

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Object-Oriented Approach to Systems

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Object-Oriented Approach (continued)
Object-oriented analysis (OOA)
Defines types of objects users deal with
Shows use cases are required to complete tasks
Object-oriented design (OOD)
Defines object types needed to communicate with people
and devices in system
Shows how objects interact to complete tasks
Refines each type of object for implementation with specific
language of environment
Object-oriented programming (OOP)
Writing statements in programming language to define what
each type of object does

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Class Diagram Created During OO
Analysis

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SDLC Variations
Many variations of SDLC in practice
Based on variation of names for phases
No matter which one, activities/tasks are similar
Some increase emphasis on people
User-centered design, participatory design
Sociotechnical systems
Some increase speed of development
Rapid application development (RAD)
Prototyping

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Life Cycles with Different Names for
Phases (Figure 2-20)

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Current Trends in Development
More adaptive approaches
The Unified Process (UP)
Extreme Programming (XP)
Agile Modeling
Scrum
Details on each in Chapter 16

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The Unified Process (UP)
Object-oriented development approach
Offered by IBM / Rational
Booch, Rumbaugh, Jacobson
Unified Modeling Language (UML) used primarily
for modeling
UML can be used with any OO methodology
UP defines four life cycle phases
Inception, elaboration, construction, transition

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The Unified Process (UP) (continued)
Reinforces six best practices
Develop iteratively
Define and manage system requirements
Use component architectures
Create visual models
Verify quality
Control changes

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Extreme Programming (XP)
Recent, lightweight, development approach to
keep process simple and efficient
Describes system support needed and required
system functionality through informal user stories
Has users describe acceptance tests to
demonstrate defined outcomes
Relies on continuous testing and integration,
heavy user involvement, programming done by
small teams

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Agile Modeling
Hybrid of XP and UP (Scott Ambler); has more models
than XP, fewer documents than UP
Interactive and Incremental Modeling
Apply right models
Create several models in parallel
Model in small increments
Teamwork
Get active stakeholder participation
Encourage collective ownership
Model with others and display models publicly

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Agile Modeling (continued)
Simplicity
Use simple content
Depict models simply
Use simplest modeling tools
Validation
Consider testability
Prove model is right with code

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Scrum
For highly adaptive project needs
Respond to situation as rapidly as possible
Scrum refers to rugby game
Both are quick, agile, and self-organizing
Team retains control over project
Values individuals over processes

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Tools to Support System Development
Computer-aided system engineering (CASE)
Automated tools to improve the speed and quality of system
development work
Contains database of information about system called
repository
Upper CASE – support for analysis and design
Lower CASE – support for implementation
ICASE – integrated CASE tools
Now called visual modeling tools, integrated application
development tools, and round-trip engineering tools

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CASE Tool Repository Contains All
System Information

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Summary
System development projects are organized
around the systems development life cycle
(SDLC)
Some projects use a predictive approach to the
SDLC, and others use a more adaptive approach
to the SDLC
SDLC phases include project planning, analysis,
design, implementation, and support

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Summary (continued)
In practice, phases overlap, and projects contain
many iterations of analysis, design, and
implementation
Models, techniques, and tools make up a system
development methodology
System development methodology provides
guidelines to complete every activity in the SDLC

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Summary (continued)
System development methodologies are based
on traditional approach or object-oriented
approach
Current trends include: Extreme Programming
(XP), Unified Process (UP), Agile Modeling, and
Scrum
CASE tools are designed to help analysts
complete system development tasks

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